Method and apparatus for heating and cooling moving tubes

ABSTRACT

A method and apparatus for heating and cooling a large diameter moving metal tube by progressively displacing it across a heating inductor, the induction current and the moving speed of the tube being adjusted so that the tube reaches its tempering temperature as it comes out of the inductor, and progressively cooling the tube rapidly at a predetermined distance from the outlet of the inductor, the distance being selected to enable a minimum tempering time to occur outside the inductor.

United States Patent 1191 Cuvelier METHOD AND APPARATUS FOR HEATING AND COOLING MOVING TUBES [75] inventor: Michel Charles Cuvelier, Liege,

Belgium [73] Assignee: Elphiac, Charleroi, Belgium [22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,921

[30] Foreign Application Priority Data Jan. 14, 1972 Belgium 112831 [52] US. Cl 219/10.41, 219/8.5, 219/1069, 266/4 E [51] Int. Cl. H05b 5/08 [58] Field of Search 219/1041, 10.79, 10.67, 219/1069, 10.73, 59, 65, 8.5, 67, 75,158,

159; 266/4 E, 5 E, 4 R, 4 S

[56] References Cited UNITED STATES PATENTS 3,731,033 5/1973 Ory 219/7.5

[451 Mar. 12, 1974 2,935,433 5/1960 Pribyl 266 4 R 3,186,699 6/1965 Grouequess.. 266/4 S 3.720,803 3/1973 Lewis 219/1041 3,036,186 5/1962 Fliezar et 31.. 219/1069 3,143,628 8/1964 601C181] 266/4 E Primary Examiner-Bruce A. Reynolds Attorney, Agent, or Firm Raymond A. Robic; J. Ernest Kenney; Arthur Schwartz [5 7] ABSTRACT A method and apparatus for heating and cooling a large diameter moving metal tube by progressively displacing it across a heating inductor, the induction current and the moving speed of the tube being adjusted so that the tube reaches its tempering temperature as it comes out of the inductor, and progressively cooling the tube rapidly at a predetermined distance from the outlet of the inductor, the distance being selected to enable a minimum tempering time to occur outside the inductor,

6 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR HEATING AND COOLING MOVING TUBES This invention relates to a method and apparatus for heating and cooling thin-walled, large diameter metal tubes.

A method for heating horizontally moving tubes wherein the tubes to be heated are run through a heating inductor by means of an appropriate conveying means is well known. When such a method is used for instance for annealing tubes of very large diameter and of great length after welding, the annealing operation may produce unacceptable deformation of the tube. This danger is all the more significant when as the wall thickness of the tube is small. It is an object of the pres ent invention to avoid this danger.

The method and apparatus in accordance with the present invention is characterized in that a tube work piece is supported horizontally by means of rollers located at opposite ends of the inductor and, simultaneously, between two center pins associated with upright extensions ofa carriage moving horizontally along a guiding path running under the inductor, in that the inductor current and the moving speed of the tube are adjusted so that the tube progressively reaches the tempering temperature of the metal of the tube when emerging from the inductor; in that a circular sprinkler, coaxial with the inductor, is set in the path of the tube at a predetermined distance from the inductor outlet; in that the heated tube is sprinkled with a refrigerating fluid by means of said sprinkler; and in that the distance between the inductor and the sprinkler is adjusted so that the sudden cooling of the tube occurs after a time sufficient for previously obtaining tempering of the matal outside the inductor.

The invention is further exemplified in the accompanying drawings in which a preferred embodiment thereof is shown. The sole FIGURE of the drawing shows, partially in section, a tube heating apparatus according to the invention.

The apparatus comprises two lateral frames I, linked by a table 2, and supporting conical rollers 3 so arranged as to provide a free space between the concial rollers of both lateral frames. In the drawings, only one lateral frame is shown, the other being removed, so that the table 2 is shown in cross section. A heating inductor 4 is laid on the table 2 and connected to an AC. generator 5 provided with a conventional current adjusting means. The current frequency is selected as a function of the desired penetration depth of the current induced in the metal of the tube. For tubes of l to 2 meters in diameter, this frequency is in the order of 52 to 60 Hz. Under the inductor 4, there is provided a guide way, for instance a pair of horizontal rails 6, along which a carriage 7 is moved. The carriage 7 includes upright members 7 which hold two center pins 8 and 9 which are about in line with the axis of the inductor 4 and lie at opposite ends of the inductor. The rollers 3 do not interfere with the motion of the carriage 7 along the rails 6, in spite of the pins 8 and 9, since the roller spindles are fixed only to one side in one of the frames 1. The carriage 7 is driven by a geared-down motor 10 equipped with speed adjusting means, for example, by means of a master screw 11. A circular sprinkler 12, coaxial with the inductor 4, is mounted at a certain distance from the latter. The sprinkler is connected to a pipe 13 and fed with a refrigerating fluid such as water,

the inlet of which is controlled by valve 14. The distance between the sprinkler l2 and the inductor 4 is adjustable by means of, for example, three screws 15.

To carry out the method in accordance with the invention, the tube 16 to be heated is placed on the conveyor formed by the concial rollers 3 and is clamped between the center pins 8 and 9. The carriage 7 is set in starting position and the generator 5 and the geareddown motor driving the master screw 11 are switched on. The current in the inductor 4 and the speed of the tube are adjusted so that the tube 16 reaches the tempering temperature of the metal of the tube as the latter reaches the exit end of the inductor 4. Soon after, the tube 16 is suddenly cooled by the sprinkler 12. The delay must be sufficient to enable sufficient time for obtaining tempering of the metal to take place, but must be as short as possible so as to restrict to a minimum length the hot area of the tube-where the metal strength is very weak, since deformation and warpage could easily occur. The requried delay is set up by means of screws 15 which enable adjustment of the distance of the sprinkler from the exit end of the inductor. Depending upon the size of the tube and the metal in volved, the tempering time required is easily determined and will need to be determined for every different type of workpiece in any event. Adjustment by screws 15 of the distance between the exit end of the inductor 4 and the sprinkler l2 achieves the desired time delay between the time that portion of the tube reaching tempering temperature emerges from the inductor and the time at which that portion is cooled by the sprinkler.

When the rear end of the tube 16 reaches the sprinkler 12, it is necessary to take some precautions for cooling the rear end of the tube in the same manner as the rest of the tube in order to avoid the refrigerating fliud, generally water, from being splashed in large quantity inside the inductor 4. For so doing, at least the center point 9 supporting the rear end of the tube 16 to be heated is provided with a sleeve 17, the diameter of which is the same as that of tube 16 and which extends coaxial therewith. This sleeve may be made either ofinsulating material or of a metal such as copper. The wall thickness of this sleeve 17 is preferably smaller than the one required for full depth penetration of the electric induced current.

The sleeve 17 may be cooled by water, particularly if it is made of a magnetic material such as steel. Water cooling is moreover used for all other parts of the apparatus which are susceptible of being inadvertently heated by any heat source. The length of the sleeve 17 depends in part on the length of the ring of refrigerating fluid produced by the sprinkler 12.

The length of the sleeve 17 depends on the various operating parameters surrounding the heating and cooling of a particular tubular workpiece. The length will usually depend on the speed of travel of the carriage for a particular workpiece, and the normal time delay needed to shut off the flow of cooling fluid once the tubular workpiece has progressed through the sprinkler. Preferably, the sleeve is of sufflcient length to enable the stopping of the carriage and the shutting off of the cooling fluid before the free end of the sleeve passes completely through the sprinkler after the tube workpiece itself has been cooled.

The invention has been described in accordance with a preferred embodiment; it is to be understood that the description is exemplary only and that it should not be considered to limit the invention beyond what is set forth in the claims below.

I claim:

1. A method for inductively heating and subsequently cooling a large diameter metallic tubular workpiece comprising:

a. supporting a large diameter metal tube horizontally on conveyor rollers located outside of and adjacent both ends of an annular, axially extending inductor heater spplied by a variable current source;

b. fixing the position of said tube between upright extensions of a movable carriage having speed control means, the carriage being movable horizontally beneath said inductor to advance the tube by means of said upright extensions axially through the heater at an adjustable rate of speed, the heater being located between the upright extensions of the carriage, and moving said tube axially by means of said carriage progressively through said inductive heater;

c. adjusting the current supply to said inductive heater and speed of travel of said carriage whereby the temperature of the tube is raised to its tempering temperature over that portion reaching the exit end of the inductor;

d. adjustably mounting a circular sprinkler coaxially with the inductor and spaced from its exit end with respect to the direction of tube travel through the inductor, the adjustable mounting enabling the distance between the exit end of the inductor and the sprinkler to be varied;

e. progressively advancing the tube entirely through the sprinkler after it leaves the inductor;

f. circulating cooling fluid through the sprinkler and on to the tube to rapidly cool the tube advanced therethrough;

g. adjusting the distance between the exit end of the inductor heater and said sprinkler whereby rapid cooling of the tube occurs after a minimal time sufficient to achieve tempering of the tube outside the inductive heater.

2. Apparatus for heating and cooling large diameter metal tubes comprising:

a. an annular inductor heating means for heating tubular workpieces horizontally and progressively advanced axially through said inductor, said inductor having a variable source of current supply;

b. means for varying the current supply to said inductor for regulating the heating applied to a workpiece;

c. roller conveyor means for supporting tubular workpieces advanced through said inductor, said roller conveyor means being located outside of and spaced from both ends of said inductor;

d. a carriage means axially movable horizontally beneath said inductor, said carriage including upwardly extending members, the inductor heater being located in an area between said members, and means for axially fixing the position of a tubular workpiece between said members;

e. variable speed drive means for said carriage;

f. means for adjusting the speed of said carriage drive means;

g. a sprinkler coaxially located adjacent the exit end of said inductor and adjustably mounted with respect to said heater whereby the distance between the exit of said heater and the sprinkler can be varied;

h. means for varying the distance between the exit end of said inductor and said sprinkler, and means for controllably supplying cooling fluid for circulation through said sprinkler;

i. whereby the inductor current supply, the carriage drive rate, and the distance between the exit end of the inductor and the sprinkler can be adjusted such that a metal tubular workpiece progressively advanced through said inductor by said carriage means reaches tempering temperature just as it reaches the exit end of the inductor and thereafter may be progressively rapidly cooled after a desired minimal time interval sufficient to achieve tempering of the tubular workpiece between the time it leaves the inductor heater and the time it is rapidly cooled.

3. The apparatus of claim 2 wherein the means recited under ((1) for axially fixing the position of a tubular workpiece further includes a shielding sleeve element forming a coaxial, rearwardly extending extension of a tubular workpiece so fixed whereby cooling fluid is prevented from entering the inductor heater when the tubular workpiece is completely advanced therethrough and through the sprinkler.

4. The apparatus of claim 2 wherein said roller conveyor in (c) comprises multiple, laterally spaced roller pairs between which said carriage upright extensions pass when the tubular workpiece supported thereby is advanced through the inductor and sprinkler.

5. The apparatus of claim 2 wherein the said means in (d) for axially fixing the position of the workpiece comprises axially extending pin elements engaging opposite ends of the workpiece, the pin elements being secured to the upright members in cantelever fashion.

6. In combination with an inductor heater for tubular, metallic workpieces, and a sprinkler fluid cooling means located adjacent the exit end of said heater, means for advancing the tubular workpieces progressively through the inductor heater at a controllable rate, and shielding sleeve means associated with said advancing means, said sleeve means forming a coaxial, rearwardly projecting extension of the workpiece to prevent cooling fluid from entering the inductor after the workpiece has passed the sprinkler and until the sprinkler has been shut off. 

1. A method for inductively heating and subsequently cooling a large diameter metallic tubular workpiece comprising: a. supporting a large diameter metal tube horizontally on conveyor rollers located outside of and adjacent both ends of an annular, axially extending inductor heater spplied by a variable current source; b. fixing the position of said tube between upright extensions of a movable carriage having speed control means, the carriage being movable horizontally beneath said inductor to advance the tube by means of said upright extensions axially through the heater at an adjustable rate of speed, the heater being located between the upright extensions of the carriage, and moving said tube axially by means of said carriage progressively through said inductive heater; c. adjusting the current supply to said inductive heater and speed of travel of said carriage whereby the temperature of the tube is raised to its tempering temperature over that portion reaching the exit end of the inductor; d. adjustably mounting a circular sprinkler coaxially with the inductor and spaced from its exit end with respect to the direction of tube travel through the inductor, the adjustable mounting enabling the distance between the exit end of the inductor and the sprinkler to be varied; e. progressively advancing the tube entirely through the sprinkler after it leaves the inductor; f. circulating cooling fluid through the sprinkler and on to the tube to rapidly cool the tube advanced therethrough; g. adjusting the distance between the exit end of the inductor heater and said sprinkler whereby rapid cooling of the tube occurs after a minimal time sufficient to achieve tempering of the tube outside the inductive heater.
 2. Apparatus for heating and cooling large diameter metal tubes comprising: a. an annular inductor heating means for heating tubular workpieces horizontally and progressively advanced axially through said inductor, said inductor having a variable source of current supply; b. means for varying the current supply to said inductor for regulating the heating applied to a workpiece; c. roller conveyor means for supporting tubular workpieces advanced through said inductor, said roller conveyor means being located outside of and spaced from both ends of said inductor; d. a carriage means axially movable horizontally beneath said inductor, said carriage including upwardly extending members, the inductor heater being located in an area between said members, and means for axially fixing the position of a tubular workpiece between said members; e. variable speed drive means for said carriage; f. means for adjusting the speed of said carriage drive means; g. a sprinkler coaxially located adjacent the exit end of said inductor and adjustably mounted with respect to said heater whereby the distance between the exit of said heater and the sprinkler can be varied; h. means for varying the distance between the exit end of said inductor and said sprinkler, and means for controllably supplying cooling fluid for circulation through said sprinkler; i. whereby the inductor current supply, the carriage drive rate, and the distance between the exit end of the inductor and the sprinkler can be adjusted such that a metal tubular workpiece progressively advanced through said inductor by said carriage means reaches tempering temperature just as it reaches the exit end of the inductor and thereafter may be progressively rapidly cooled after a desired minimal time interval sufficient to achieve tempering of the tubular workpiece between the time it leaves the inductor heater and the time it is rapidly cooled.
 3. The apparatus of claim 2 wheRein the means recited under (d) for axially fixing the position of a tubular workpiece further includes a shielding sleeve element forming a coaxial, rearwardly extending extension of a tubular workpiece so fixed whereby cooling fluid is prevented from entering the inductor heater when the tubular workpiece is completely advanced therethrough and through the sprinkler.
 4. The apparatus of claim 2 wherein said roller conveyor in (c) comprises multiple, laterally spaced roller pairs between which said carriage upright extensions pass when the tubular workpiece supported thereby is advanced through the inductor and sprinkler.
 5. The apparatus of claim 2 wherein the said means in (d) for axially fixing the position of the workpiece comprises axially extending pin elements engaging opposite ends of the workpiece, the pin elements being secured to the upright members in cantelever fashion.
 6. In combination with an inductor heater for tubular, metallic workpieces, and a sprinkler fluid cooling means located adjacent the exit end of said heater, means for advancing the tubular workpieces progressively through the inductor heater at a controllable rate, and shielding sleeve means associated with said advancing means, said sleeve means forming a coaxial, rearwardly projecting extension of the workpiece to prevent cooling fluid from entering the inductor after the workpiece has passed the sprinkler and until the sprinkler has been shut off. 